Key Takeaways:
- Sidereal time is a measurement of Earth's rotation relative to distant stars.
- A sidereal day is the time taken for a star to return to the same position in the sky.
- Solar time differs from sidereal time due to Earth's orbital motion around the Sun.
- A solar day is approximately four minutes longer than a sidereal day because of the Earth's extra rotation needed to realign with the Sun.
Sidereal time (left) is measured with respect to background stars while solar time references the Sun. Earth needs to rotate nearly an extra degree for the Sun to pass the reference point; this accounts for almost 4 more minutes in a solar day than a sidereal day. Astronomy: Roen Kelly
Sidereal time literally means “time by the stars.” A sidereal day is a measurement of one rotation of Earth referenced to distant background stars — think of this as the amount of time it takes a particular star to come back to the same place in our sky the next night.
